in the amd way…
i have r9-290 and works fine with UE4.
pci 2.0 can limit you if you buy a top card, but i think pci3.0 cards are compatible with 2.0 (if im wrong someone rectified that), and thinking in upgrade later your cpu/mb you can buy a 380 or any new better card. Its price its a problem with AMD you get more for less money.